Skin well-being in diabetes: Role of macrophages

Research progress related to thermosensitive hydrogel dressings in wound healing: a review

Wound healing is a dynamic and complex process in which the microenvironment at the wound site plays an important role. As a common material for wound healing, dressings accelerate wound healing and prevent external wound infections. Hydrogels have become a hot topic in wound-dressing research because of their high water content, good biocompatibility, and adjustable physical and chemical properties. Intelligent hydrogel dressings have attracted considerable attention because of their excellent environmental responsiveness. As smart polymer hydrogels, thermosensitive hydrogels can respond to small temperature changes in the environment, and their special properties make them superior to other hydrogels. This review mainly focuses on the research progress in thermosensitive intelligent hydrogel dressings for wound healing. Polymers suitable for hydrogel formation and the appropriate molecular design of the hydrogel network to achieve thermosensitive hydrogel properties are discussed, followed by the application of thermosensitive hydrogels as wound dressings. We also discuss the future perspectives of thermosensitive hydrogels as wound dressings and provide systematic theoretical support for wound healing.

Exosomes: A Promising Strategy for Repair, Regeneration and Treatment of Skin Disorders

The skin is the organ that serves as the outermost layer of protection against injury, pathogens, and homeostasis with external factors; in turn, it can be damaged by factors such as burns, trauma, exposure to ultraviolet light (UV), infrared radiation (IR), activating signaling pathways such as Toll-like receptors (TLR) and Nuclear factor erythroid 2-related factor 2 (NRF2), among others, causing a need to subsequently repair and regenerate the skin. However, pathologies such as diabetes lengthen the inflammatory stage, complicating the healing process and, in some cases, completely inhibiting it, generating susceptibility to infections. Exosomes are nano-sized extracellular vesicles that can be isolated and purified from different sources such as blood, urine, breast milk, saliva, urine, umbilical cord bile cells, and mesenchymal stem cells. They have bioactive compounds that, thanks to their paracrine activity, have proven to be effective as anti-inflammatory agents, inducers of macrophage polarization and accelerators of skin repair and regeneration, reducing the possible complications relating to poor wound repair, and prolonged inflammation. This review provides information on the use of exosomes as a promising therapy against damage from UV light, infrared radiation, burns, and skin disorders.

Advances in Zebrafish for Diabetes Mellitus with Wound Model

Diabetic foot ulcers cause great suffering and are costly for the healthcare system. Normal wound healing involves hemostasis, inflammation, proliferation, and remodeling. However, the negative factors associated with diabetes, such as bacterial biofilms, persistent inflammation, impaired angiogenesis, inhibited cell proliferation, and pathological scarring, greatly interfere with the smooth progress of the entire healing process. It is this impaired wound healing that leads to diabetic foot ulcers and even amputations. Therefore, drug screening is challenging due to the complexity of damaged healing mechanisms. The establishment of a scientific and reasonable animal experimental model contributes significantly to the in-depth research of diabetic wound pathology, prevention, diagnosis, and treatment. In addition to the low cost and transparency of the embryo (for imaging transgene applications), zebrafish have a discrete wound healing process for the separate study of each stage, resulting in their potential as the ideal model animal for diabetic wound healing in the future. In this review, we examine the reasons behind the delayed healing of diabetic wounds, systematically review various studies using zebrafish as a diabetic wound model by different induction methods, as well as summarize the challenges and improvement strategies which provide references for establishing a more reasonable diabetic wound zebrafish model.

Glucose and MMP-9 dual-responsive hydrogel with temperature sensitive self-adaptive shape and controlled drug release accelerates diabetic wound healing

Chronic diabetic wounds are an important healthcare challenge. High concentration glucose, high level of matrix metalloproteinase-9 (MMP-9), and long-term inflammation constitute the special wound environment of diabetic wounds. Tissue necrosis aggravates the formation of irregular wounds. All the above factors hinder the healing of chronic diabetic wounds. To solve these issues, a glucose and MMP-9 dual-response temperature-sensitive shape self-adaptive hydrogel (CBP/GMs@Cel&INS) was designed and constructed with polyvinyl alcohol (PVA) and chitosan grafted with phenylboric acid (CS-BA) by encapsulating insulin (INS) and gelatin microspheres containing celecoxib (GMs@Cel). Temperature-sensitive self-adaptive CBP/GMs@Cel&INS provides a new way to balance the fluid-like mobility (self-adapt to deep wounds quickly, approximately 37 °C) and solid-like elasticity (protect wounds against external forces, approximately 25 °C) of self-adaptive hydrogels, while simultaneously releasing insulin and celecoxib on-demand in the environment of high-level glucose and MMP-9. Moreover, CBP/GMs@Cel&INS exhibits remodeling and self-healing properties, enhanced adhesion strength (39.65 ± 6.58 kPa), down-regulates MMP-9, and promotes cell proliferation, migration, and glucose consumption. In diabetic full-thickness skin defect models, CBP/GMs@Cel&INS significantly alleviates inflammation and regulates the local high-level glucose and MMP-9 in the wounds, and promotes wound healing effectively through the synergistic effect of temperature-sensitive shape-adaptive character and the dual-responsive system.

•

The hydrogel with temperature-sensitive adaptive shape can fill irregular wounds.

•

The hydrogel on-demand releases drugs responding to diabetic wound environment.

•

The hydrogel significantly accelerated diabetic wound healing.

Alternative polarization of resident macrophages improves hyperglycemia-associated male infertility

Recent studies have demonstrated that hyperglycemia induces inflammation in male reproductive system to cause sperm damages and infertility, which may be associated with re-polarization of tissue macrophages from an anti-inflammation M2-like subtype to a pro-inflammation M1-like subtype. However, the underlying mechanisms are not fully determined and a practical approach to interfere with the progression of infertility is lacking. Here, we transduced the testicular macrophages back to the M2-like phenotype with adeno-associated viruses carrying an M2-trigger, Jumonji domain-containing protein D3 (JMJD3), under a macrophage-specific CD68 promoter (CD68p-JMJD3), in streptozotocin-induced diabetic mice. We found that JMJD3-induced M2-polarization of testicular macrophages significantly improved the mating capability of diabetic male mice. The diabetes-induced impairment of the motility of spermatozoa and the decreases in the serum and testicular testosterone levels were both significantly alleviated in CD68p-JMJD3-treated diabetic mice. Thus, our study proposes a practical strategy to treat hyperglycemia-associated infertility.

Ex vivo tolerization and M2 polarization of macrophages dampens both pro- and anti-inflammatory cytokine production in response to diabetic wound fluid stimulation

Monocytes/macrophages play a prominent role in cutaneous wound healing. Persistent inflammation in diabetic wounds is associated with the inability of monocytic cells to switch from a phagocytic M1 (classically activated) to an anti-inflammatory, pro-regenerative M2 (alternatively activated) phenotype and as consequence, the proliferative phase of healing does not commence. A targeted cell therapy approach could potentially restore the pathological wound microenvironment through paracrine signalling to enable healing. This study investigated whether in vitro pre-treatment of monocytic (J774.1 A) cells - using a combination of endotoxin-induced immune tolerance (Pam3CSK4) and M2 polarization (IL-4) - could make these cells impervious to the pathological wound microenvironment and enhance the release of anti-inflammatory cytokines/growth factors. The effect of Pam3CSK4-induced tolerance and IL-4-associated polarization was assessed independently and in combination, on the expression of intracellular (flow cytometry) and secreted (ELISA) cytokines (TNF-ɑ, IL-6, IL-10, TGF-β) with and without re-stimulation to define the optimal pre-treatment conditions. Successive pre-treatment approach consisting of endotoxin tolerance followed by IL-4 priming, dampened TNF-ɑ release and induced intracellular TGF-β production upon re-stimulation. To mimic a chronic wound microenvironment, the J774A.1 monocytes were differentiated into macrophages using GM-CSF prior to pre-treatment (optimal condition) and subsequently exposed to diabetic wound fluid. The data demonstrated that in the presence of wound fluid, the successive pre-treatment, promoted M2 polarization (CD206) of monocytic cells and significantly dampened the intracellular production of both pro-inflammatory (TNF-ɑ, IL-6) and anti-inflammatory (IL-10, TGF-β) cytokines.